Was Séralini’s protocol flawed?

Questions have been raised about Séralini’s study
protocol. But Séralini designed his study to be comparable with Monsanto’s[1]
– thus the design was similar. While the Monsanto study used twice the sample
size (rats per group) as Séralini, the Monsanto authors only analyzed blood and
urine from half of the animals – the same number of sampled animals as in
Séralini’s study. Both studies used the same rat strain – the Sprague-Dawley.

Séralini added elements that made his study more detailed
than Monsanto’s. He tested three levels of GM maize exposure, compared with Monsanto’s
two, and measured a larger number of effects more often. Furthermore, Séralini
added additional treatment groups, namely NK603 maize not treated with Roundup,
and Roundup exposure alone (in drinking water). This was done in an effort to
ascertain whether any ill effects observed were due to the GMO, Roundup or a
combination of the two. Again, this is an issue that industry and regulators
have failed to address.

The key difference between the studies was thus not in
research protocol, but in breadth of analysis and study duration. Crucially,
Séralini’s study lasted two years, as compared with Monsanto’s 90 days. This
proved to be important because in Séralini’s study, the first tumours only
became visible four months into the experiment – a month after Monsanto’s study
had ended.

According to the OECD protocol for chronic toxicity
studies like Séralini’s, it is acceptable to extend such a study to two years
if scientifically justified. The unexpected tumour observations, beginning in
the 4th month, could be considered to provide justification to
extend the study length.[2]

Both studies were reviewed, accepted, and published by
the same journal – Food and Chemical Toxicology (FCT). Only Séralini’s paper
has been retracted.